"As soon as I did it, I knew what it was," said Clevenger, who missed a month last season because of a right oblique strain. "It was a lot worse than last year, pain-wise. Last year, I did it in the last swing of (batting practice). I went up into the clubhouse and I was a little tight. But (Saturday), I just felt like someone stuck a knife in my side and knocked the breath out of me."
The Cubs also agreed Sunday to a minor league deal with reliever Kevin Gregg. The right-hander had 23 saves with the Cubs in 2009 and was replaced as the closer by Carlos Marmol.
Gregg was 3-2 with a 4.95 ERA for Baltimore last season. He was with the Los Angeles Dodgers in spring training and was assigned to their minor league camp late last month.